Comparative analysis of polycyclic aromatic sulfur heterocycles (PASHs) in PM2.5 from Xi’an, China and Yokohama, Japan: pollution characteristics and source attribution

Polycyclic aromatic sulfur heterocycles (PASHs) sulfur-containing analogues of polycyclic aromatic hydrocarbons (PAHs) are emerging atmospheric pollutants of concern due to their potential toxicity and environmental persistence. This study presents the first comparative analysis of PASHs in PM 2.5 between two representative East Asian cities: Xi’an, China, and Yokohama, Japan. Ambient PM 2.5 samples were collected from July 2022 to July 2023, and four PASHs compounds were quantified using gas chromatography tandem mass spectrometry (GC–MS/MS). Concentrations, seasonal variations, and emission sources were systematically analyzed. The results showed that the annual mean PASHs concentration in Xi’an (156.6 pg/mg) was significantly higher than that in Yokohama (102.6 pg/mg). Source apportionment using the Positive Matrix Factorization (PMF) model identified four major pollution sources in each city, revealing notable differences in source composition between the two countries. This study advances the understanding of the atmospheric behavior and origins of PASHs in East Asian urban environments and highlights cross-regional differences in their pollution profiles.